Process for the magnetic treatment of iron ores



Fatented July 5, E932 assreuon no xnrsm wrnnnrrr n,- or nussmnoar, enem PCESS FOR T MAGNEFQIC TREATMNTOE IRON ORES We Erawlng. Application filed Qctober 8, 1931. Serial No. 567,751,:1116. in Germany August 10,1928.

It is hown that mineral iron of feebly magnetic red andbrown theiron is present in the highest stage of oin'dation, can be converted into the ferro- 'magnetic form by reduction to lower stages of oxidation, whereby the subsequent electromagnetic concentration is facilitated; The desired stage of oxidation according to this method of operation is Fe O It is not possible however to avoid all possible stages of oxidation being passed until metal is reached in the course of the reduction and as the capacity of these various substances for magnetization varies greatly, the subsequent magnetic separation yields a substance that has an unsatisfactory composition.

' lit has been found by research that, in addition to the ferromagnetic F6804, a ferromagnetic form of F6203 is also possible, the permeabilityof which is even higher than that of'Fe O According to the invention the ferro-magnetic Fe t) 1s made usable for the practical concentration of iron ores by conducting the reducing operation in such manner that the formation of the ferro-magnetic Fe O can take place in the ores. My

experiments with various iron ores have.

shown that the ferro-magn'etic Fe O can be produced by re oxidizing the ores in-gvhich the iron is present in the highest stage of xidation, as; for example, in redand brown .ron ores, after they have been subjected to ;he well known process of reduction at tem )eratures of from 400 to 700 C. and mainaining temperatures of from 220 to 500 (1., luring this om'dation. It has also been bund that the prejudicial effect to the mag letic preparation due to over-reduction, such s frequently occurs during the reducing reatement by producing free protoxide, is ffectually overcome and nullified by. such eoxidation treatment.

Thus, according to the invention, the highat stage of oxidation in the ores is brought ack from the lower stages of oxidation aached after the well known reducing opertion, by re-oxidation, a suitablei'ange of imperatures being maintained.

The following example will serve to exiron ores, in which magnetically separated on plain theprocess and also demonstrate the practical advantages obtained A German red iron ore Was-"taken and treated as follows 1. Direct magnetic separation of the unroasted ore. I

2.' Reduction of the ore to low stages of oxidation with subsequent magnetic separation of the roasted material.

3. Reduction of theoxidation, then oxidation of the roasted ma terial for the purpose of restoring the highest stage of oxidation, and finally magnetic separation. v

Below is given the degree of separation (55 which is generally accepted at, the present time as the measure of the concentration factor in order to characterize the resultof the 1 concentration. 7 The degree of separation for the electroagnetic separation of the unroasted sample ore was 26.2% and the exciting current of the magnetic separator was 8 amps. volts.'

For a sample of the same ore which had 1'15 been subjected to reduction at 500 C. with illuminating gas for one hour, and electro- A the same separator, "the degree of separation for the pure magnetic separation was 25.9% and for the so total concentration, which includes the concentration effected by the roasting 39.8%. It

W8. S 'f01111d possible. to reduce the exciting current to 0.24 am s. I

For a sample 0 the sam orewhichvwas e5 (subjected to a reduction an afterwards oxidized in a current of air at a temperature between 500 and 300 0., the extent of electro-magnetic separation rose on the subsequent concentration of this reduced product 90 to 38.8 while in conjunction with'the concentration produced by the expulsion of water of crystallizatiomcarbonic acid, and thelike,'dur ng tlie reduction, it rose to a total of J 50.2%. In this case it was possible to re- 95 .duce the excitation of the separator to 019 amps. I t'llhus among the advantages of the process are that by it the concentration output or factor. is increased, it is possible to use clieapore to low stages of 4 ores by current.

er magnetic separators with weak magnetic fields, and there is a saving in the exciting The rocess can also be used when mixtures o term-magnetic mineral iron occurs with red'orbrown ironstone.

The process of treating red-and brown iron the magneticmethodfor the purpose-set forth, which consists in subjecting the ore to a reducin treatment in the presence'of sufficient car onaceous material and for asuflicient period to transform the iron compounds of the ore into ferro-magnetic Fe O then subjecting'the ore to reoxidation in the presence of a gaseous oxidizing agentemperatures maintained substantially at with'n the range of from 220 to 500 C. for a suflicient period of time to convert the reduced ore of loweroxidation stage to ferromagnetic Fe O and then sub ecting the 1 treated ore tomagnetic separation -WALTER LriYKEN; 

